Allen-Bradley 1756-OF6CI/A Replacement for ControlLogix

Product Overview

Allen-Bradley 1756-OF6CI/A Replacement for ControlLogix: Smooth Migration & Legacy System Upgrade

The Allen-Bradley 1756-OF6CI/A is a 6-channel isolated analog output module designed for the ControlLogix platform. As Rockwell Automation continues to evolve its product portfolio, many facilities operating legacy ControlLogix 1756 chassis are facing the challenge of sourcing reliable replacements for aging or discontinued I/O modules. The 1756-OF6CI/A remains one of the most sought-after analog output modules for process control applications — delivering ±10V, 0–10V, 0–20mA, and 4–20mA output ranges with full channel-to-channel isolation, making it indispensable in environments where signal integrity and loop independence are critical.

Whether you are replacing a failed module in a running production line, upgrading from an older 1756-series analog output card, or migrating from a legacy PLC-5 or SLC 500 system to a modern ControlLogix architecture, the 1756-OF6CI/A provides a proven, drop-in compatible solution that minimizes engineering rework and commissioning time.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful migration to or around the 1756-OF6CI/A typically involves more than swapping a single module. In practice, field engineers upgrading from PLC-5 or SLC 500 platforms to ControlLogix will also need to address the broader system architecture. The 1756-L8x or 1756-L7x ControlLogix controllers serve as the central processing unit in the new chassis, replacing older PLC-5/40 or SLC 5/05 processors. The controller communicates with the 1756-OF6CI/A and other I/O modules over the 1756 backplane, eliminating the need for legacy DH+ or Remote I/O networks.

For facilities retaining existing field wiring, the 1756-TBCH removable terminal block allows technicians to pre-wire the terminal assembly before the module arrives, dramatically reducing installation downtime. In multi-chassis or distributed I/O configurations, the 1756-EN2T EtherNet/IP communication module enables the ControlLogix system to communicate across plant networks, replacing older 1756-ENBT adapters and supporting Device Level Ring (DLR) topologies.

When migrating analog signal loops from legacy systems, signal conditioning may be required. The 1756-OF6CI/A’s per-channel isolation eliminates ground loop issues common in older non-isolated output modules, but facilities with long cable runs or noisy environments may also benefit from DIN-rail mounted signal isolators between the module’s RTB and field devices such as control valves, variable frequency drives (VFDs), or positioners.

On the input side, the companion 1756-IF16 or 1756-IF8 analog input modules are commonly installed in the same chassis to complete the process loop — receiving 4–20mA feedback signals from transmitters, flow meters, or pressure sensors. For digital I/O requirements in the same retrofit project, the 1756-IB16 and 1756-OB16E discrete I/O modules are standard additions to the 1756 chassis build.

Power infrastructure is equally important. The 1756-PA75 or 1756-PB75 chassis power supply must be sized to support the total module load, including the 1756-OF6CI/A’s backplane current draw. In larger chassis configurations (13-slot or 17-slot 1756-Axx chassis), redundant power supply modules may be required to meet uptime requirements. Finally, for programming and firmware management, the 1756-USB or 1784-U2DHP USB-to-DH+ programming cable is essential for technicians transitioning from RSLogix 5 to Studio 5000 during the migration commissioning phase.

Retrofit Guidance FAQ

Q: Can the 1756-OF6CI/A be installed in any slot of a 1756 chassis?
A: Yes. The module occupies a single slot in any 1756-Axx chassis (4, 7, 10, 13, or 17 slot). Slot assignment is configured in Studio 5000 Logix Designer and does not affect module functionality.

Q: What terminal block is required for field wiring?
A: The 1756-OF6CI/A uses the 1756-TBCH (cage clamp) or 1756-TBS6H (screw clamp) removable terminal block. These RTBs are sold separately and allow pre-wiring before module installation, minimizing downtime during hot-swap replacement.

Q: Is the module compatible with EtherNet/IP and ControlNet?
A: The 1756-OF6CI/A communicates over the ControlLogix backplane. The chassis communication protocol (EtherNet/IP or ControlNet) is determined by the communication module (e.g., 1756-EN2T or 1756-CN2) installed in the same chassis. The analog output module itself is protocol-agnostic at the field wiring level.

Q: Can this module replace a non-isolated analog output module like the 1756-OF8?
A: Functionally yes, with configuration changes in Studio 5000. The 1756-OF6CI/A provides 6 isolated channels versus the 1756-OF8’s 8 non-isolated channels. If your application requires more than 6 channels, two 1756-OF6CI/A modules can be used. Wiring must be updated to match the new RTB pinout.

Q: What programming software is required?
A: Studio 5000 Logix Designer (v20 or later recommended). If migrating from RSLogix 5000, existing AOP (Add-On Profile) configurations for the 1756-OF6CI/A are compatible. Legacy RSLogix 5 or RSLogix 500 programs require conversion using the Migration Toolkit.

Q: How is the module powered?
A: The 1756-OF6CI/A draws power from the 1756 chassis backplane. No external 24VDC field power is required for the module itself, though field devices (valves, drives) connected to the output channels require their own loop power supply.

Q: What is the physical installation space requirement?
A: The module occupies one standard 1756 chassis slot. Depth clearance of approximately 4.7 inches (119mm) is required behind the chassis for backplane connector engagement. Standard 1756 chassis mounting dimensions apply.

Warranty Assurance

Every 1756-OF6CI/A shipped by TOPNLMS is covered by a 12-month warranty from the date of delivery. Prior to shipment, each module undergoes functional verification including backplane communication check, channel output calibration verification, and visual inspection for physical integrity. Modules are shipped in anti-static packaging with appropriate cushioning to prevent transit damage.

In the event of a confirmed defect within the warranty period, TOPNLMS will arrange replacement or repair at no additional cost to the buyer. Our technical support team is available to assist with installation questions, compatibility verification, and commissioning guidance. Typical response time for warranty claims is within 1–2 business days.

For bulk procurement, OEM integrators, and system integrators requiring multiple units for a retrofit project, volume pricing and expedited shipping options are available. All orders include a certificate of conformance upon request.

Stock is maintained in our Xiamen warehouse for immediate dispatch. Standard international shipping lead time is 3–7 business days depending on destination. Express DHL/FedEx options are available for urgent replacement requirements.

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